Take the following ingredients: the industrial shell of a disused freight railway suspended 30 feet above the street, slowly decaying in the 21st century; several well-known neighbourhoods, unsatisfactorily separated by wide roads and semi-industrial scrub; and New York’s intrinsic flair for improbable daring and boldness. Now, add an impeccable arrangement of trees, shrubs and other plants, alongside hardwood benches and sunloungers, with occasional plazas and playgrounds, and you get the final result: the completed High Line, largely funded by private money, one of the most expensive parks per acre in human history – and almost certainly the quickest to turn that investment into civic profit.

The genius of the High Line, as is often the case with great ideas, was satisfying a desire that had simmered only subconsciously. It is a viewing point, a sunbathing haven, an assembly for street food vendors, a tourist attraction, an idler’s idyll, a garden and also – crucially – a means of getting from A to B. Far from being dourly utilitarian, that usefulness is at the heart of the triumph. The High Line has made us think differently about public space.

Fifteen years ago, I used to live two short blocks away from the southern tip of the High Line. Yet I almost never walked north along the route the park now follows. Why? As I’ve written in this column before, urban areas often “point” one way rather than the other. My old street “faced” south towards the West Village, rather than north towards Chelsea. When places aren’t enticingly linked up, we tend simply to find amenities in another direction. The aggregate of many such subtly constrained individual lives is a correspondingly diminished city.

But on a recent Sunday, ambling uptown with a friend, taking the High Line not only felt natural, it was obvious. Why wouldn’t you take a few steps above street level, escaping the traffic while gorging on the cityscape? We got to where we needed to be; an aesthetic and social experience, a bonus, was thrown into the bargain. The High Line has realised the city planner’s Holy Grail: it has both created space and reduced distance.

By chance, that weekend marked the opening of the park’s newest and final leg, where the High Line changes direction – now east-west, rather than north-south – with unbroken views of the Hudson River to one side and midtown on the other. It has perked up the whole area. High Line yoga studios prepare clients for post-workout sustenance at “under the High Line” cafés. The park’s flanks have become a global talent competition for residential and commercial architects, commissioned by developers capitalising on a frenzy of demand. Even though the park inevitably looks over some new properties, the term High Line is real-estate gold dust. Privacy? What privacy? People want to join the party.

No wonder other cities are clamouring to create imitations to transform the urban environment. In terms of ambition London may top the list. In principle, it sounds irresistible: a garden bridge over the Thames. The designer is Thomas Heatherwick, whose cauldron lit up the Olympic opening ceremony; Boris Johnson is an enthusiastic supporter and mayoral sponsor.

The concept image for Skycycle. Image: Foster & Partners.

It is less clear, however, that the Garden Bridge will leave a High Line-style legacy. The cost is already spiralling. In June 2013, it was widely reported to be £60m; now, it’s estimated at £175m. London may be better served by embracing a different transport infrastructure project, one that follows the High Line principle of transforming what is already there. This is SkyCycle. The plan, which is being developed by Foster & Partners, Exterior Architecture and Space Syntax, is to construct cycle highways that follow London’s existing suburban railway corridors – a wide, secure deck constructed above the trains. The result would be a commuter paradise: 220 kilometres of safe, car-free cycle routes accessible from 200 entrance points. The developers estimate that 5.8 million people could reach the network within ten minutes of their front door; all of London’s terminals would be within one hour’s cycling. The cost? Between £8bn and £10bn. By comparison, Crossrail, London’s new railway line, will cost close to £16bn.

SkyCycle would certainly be eye-catching – a cycle superhighway suspended in the air. Yet it also responds to one of London’s great problems: allowing people to move around affordably and efficiently. Even after the arrival of Crossrail in 2016, that challenge will only become more acute: London’s population rises by about 80,000 every year, heading towards ten million by 2030.

In an interview with the Guardian on 21 September, Peter Hendy, the head of Transport for London, described the social costs if London fails to improve its commuter infrastructure. “If you’re not able to increase transport capacity and people find accessing work impossible, you risk social unrest. You can expect trouble,” Hendy warned. “If you contemplate a London in 2030 without continuous investment . . . we will have the kind of congestion you’re looking at in Mumbai.”

A cycle highway in the sky might not be the most obvious place to begin a quest for commuter solutions and social cohesion. However, SkyCycle has the potential to apply High Line-style methodology, in a way that addresses London’s real problems.

The High Line was a victory for both imaginative ambition and applied practical thinking. The essential raw materials were already in place. It resolved issues that did exist, while creating solutions that no one had anticipated. It wasn’t a glorious folly. Other cities should follow that example but only in their own, unique ways. SkyCycle could be the best of the lot. l

Ed Smith’s latest book is “Luck: a Fresh Look at Fortune” (Bloomsbury, £8.99).

This column was originally published in the print edition of the New Statesman.